Cho, John Y. N.Newell, Reginald E.Bui, T. PaulBrowell, Edward V.Fenn, Marta A.Mahoney, Michael J.Gregory, Gerald L.Sachse, Glen W.Vay, Stephanie A.Kucsera, Tom L.Thompson, Anne M.2024-07-262024-07-261999-09-01Cho, John Y. N., Reginald E. Newell, T. Paul Bui, Edward V. Browell, Marta A. Fenn, Michael J. Mahoney, Gerald L. Gregory, et al. “Observations of Convective and Dynamical Instabilities in Tropopause Folds and Their Contribution to Stratosphere-Troposphere Exchange.” Journal of Geophysical Research: Atmospheres 104, no. D17 (1999): 21549–68. https://doi.org/10.1029/1999JD900430.https://doi.org/10.1029/1999JD900430http://hdl.handle.net/11603/34926With aircraft-mounted in situ and remote sensing instruments for dynamical, thermal, and chemical measurements we studied two cases of tropopause folding. In both folds we found Kelvin-Helmholtz billows with horizontal wavelength of ∼900 m and thickness of ∼120 m. In one case the instability was effectively mixing the bottomside of the fold, leading to the transfer of stratospheric air into the troposphere. Also, we discovered in both cases small-scale secondary ozone maxima shortly after the aircraft ascended past the topside of the fold that corresponded to regions of convective instability. We interpreted this phenomenon as convectively breaking gravity waves. Therefore we posit that convectively breaking gravity waves acting on tropopause folds must be added to the list of important irreversible mixing mechanisms leading to stratosphere-troposphere exchange.20 pagesen-USThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.Public Domainhttps://creativecommons.org/publicdomain/mark/1.0/Text